'86 F150 5.0 fuel injected with dual tanks. My rear tank will not work for anything. I have changed the tank, sending unit and the pump. The problem has not improved even slightly. After wasting all this time and money, I am very frustrated and loosing faith in my Ford (not to mention my mechanic). I know this is a common problem with our model trucks, so why is it so hard to trouble shoot. It will work very briefly but if I accelerate quickly or just let it run for a while, it will fail. Can someone PLEASE give some advise on what is causing my problem.

 

Try replacing the tank selector valve it is a round plastic housing under the cab of your truck it also serves as the fuel filter, it has about 6 plastic fuel lines going to it and no electric it is operated solely off the pressure of one tank or another making it problem prone, they run about 80 bux i think

 

[font size="1" color="#FF0000"]LAST EDITED ON 04-Jun-01 AT 09:30 AM (EST)[/font][p]I got it at http://fordpartsonline.com for $48.

=========================
1988 F-150, V8, 5.0L (302ci), 5spd, SuperCab. Shorty headers, K&N filter, MSD 6a ignition, Accel 300 8.8mm race wires, Accel supercoil, Accel rotor+cap, Bosch +4 Platinum plugs, RanchHand bumper. Soon: Dual exhaust.
http://brembs.net/cars/FordPU.html

 

Thanks for the input. I will be changing the part this week. However, I have a few more questions. Why would this valve allow one tank to work but not the other? Also, I lost the boost pump this weekend, could the other problems have put too much of a strain on it causing it to fail?

Thanks

 

If the return lines were plugged, or the value was not allowing fuel to return to the tank. That might cause the boost pump to fail.

Roger Lane
Test Analyst
Sr. Automated Test Engineer
IBP, Inc.

 

How can the fuel selector valve allow one tank to run, but not the other. It seems to me that either both or none would work. Does it get stuck or something? I just don't want to change anymore parts than I have to, but I do want my truck to finally work properly.

 

i took mine off and cleaned it. it comes apart real easy ( screws) just dont damage the diaphragm. it had a needle valve in it that can get stuck. get a can of carb cleaner and go to town. have you checked to see if you are getting electricity to the rear pump? just checking. i had about the same problem, replaced the pump but still no fuel. it was a kinked hose on the rear tank where it comes from the pump through the frame. i just loosened the tank and pulled on the hose and about 4" came out. problem solved. i feel your pain i could hear the pump running but i wasnt getting fuel to the selector valve. at least its summer right! i walked 4 times in the snow before i figured it out! just some sugestions before you spend any more money that you may not have to. dont loose faith your truck still loves you by the way the selector valve works off pressure from the pumps when you flip the switch fuel pressure pushes down (OR UP depending wich tank) the diaphragm and opens the valve to the coresponding fuel lines. if you look the lines are stacked horizontaly.2 inlets 2 outlets and 2 returns. just my 2 cents
chad




87 f-250
" if you are going to have a bear, it might as well be a grizzly"
4.9 granny tranny 4.11 gears

 

first of all, unless i missed it, you havnt told us if you can hear the rear pump running. if you cant, first things first...check the fuses (i screwed up hard once, replaced a bunch of crap and all it was was a blown fuse, yikes!!) if the fuses are good, the next easiest thing to do is crawl back there and disconnect the harness going into the tank, then put a voltage tester on it with the key on (you can get those little tester lights for $2 if you dont have something like that) and check to make sure its getting power. if its not, its likely the fuel pump relay or the selector switch are bad. thats all assuming you dont hear the pump. if you do hear the pump, check all the lines for kinks, as was said earlier, and then check all the filters. a good way to check if its the selector valve is bad is to pull the hose into it coming from the rear tank then let the pump run and see if it pours out. then put it back on and take off the hose on the other side of it. anyway, thats about all for now, let us know how it turns out.

 

Thanks to everyone. My mechanic and I have diagnosed the problem as an electrical short. He has it today tracing the wires. It finally left him on the road instead of me. It's funny how things just won't fail when you want them to. I appreciate all the help and will post the results soon hopefully.